1. Field of the Invention
The present invention relates to a solid-state image pickup device, and more particularly, it relates to a solid-state image pickup device comprising a lens for condensing light on a photodetection part having a photoelectric conversion function.
2. Description of the Background Art
A solid-state image pickup device comprising a lens for condensing light on a photodetection part having a photoelectric conversion function is known in general, as disclosed in Japanese Patent Laying-Open No. 2000-164839, for example.
FIG. 29 is a sectional view showing the structure of a solid-state image pickup device 102 according to first exemplary prior art comprising a lens, having a structure similar to that of the lens disclosed in the aforementioned Japanese Patent Laying-Open No. 2000-164839, for condensing light on a photodetection part. Referring to FIG. 29, the solid-state image pickup device 102 according to the first exemplary prior art comprises a substrate 104. A plurality of photodetection parts 105 having photoelectric conversion functions of converting incident light to charge signals are formed on the surface of the substrate 104 at prescribed intervals. These plurality of photodetection parts 105 form a photodetection region on the surface of the substrate 104. Transfer gates 106 are also provided on the surface of the substrate 104 for transferring the charge signals obtained in the photodetection parts 105 through insulator films 110a. Shielding members 107 are formed to cover the transfer gates 106 through insulator films 110b. The shielding members 107 have functions of preventing the transfer gates 106 from incidence of light. An upwardly convexed lens 109 is formed on the photodetection part 105 located between each adjacent pair of shielding member 107 for condensing light on the photodetection part 105 through the corresponding insulator film 110a. This lens 109 is so arranged that a lens center 109a thereof coincides with the center of the corresponding photodetection part 105. A flattened film 108 having a flat upper surface is formed to cover the transfer gates 106, the shielding members 107 and the lens 109. A color filter layer 111 is formed on the flattened film 108. The lens 109 thus arranged between the color filter layer 111 and the substrate 104 is referred to as an inner lens or the like dissimilarly to a microlens formed on a color filter layer.
FIG. 30 is a sectional view showing a solid-state image pickup device 122 according to second exemplary prior art comprising a lens for condensing light on a photodetection part. Referring to FIG. 30, the solid-state image pickup device 122 according to the second exemplary prior art comprises a downwardly convexed lens 119, dissimilarly to the solid-state image pickup device 102 according to the first exemplary prior art shown in FIG. 29. The downwardly convexed portion of this lens 119 is arranged between a pair of adjacent shielding members 107. A lens center 119a of the lens 119 coincides with the center of a corresponding photodetection part 105 formed on a substrate 104. A color filter layer 121 is formed above the lens 119 through a resin layer 120.
In the solid-state image pickup device 102 according to the first exemplary prior art shown in FIG. 29, however, the lens 109 is so arranged that the lens center 109a coincides with the center of the corresponding photodetection part 105, and hence it is difficult to condense light obliquely incident upon the lens 109 on the center of the photodetection part 105, as shown in FIG. 31. In this conventional solid-state image pickup device 102, optical lenses 101a and 101b set at prescribed intervals from the solid-state image pickup device 102 and an aperture stop 101c arranged between the optical lenses 101a and 101b are employed for introducing external light into the solid-state image pickup device 102 as shown in FIG. 32. At this time, light refracted by the optical lenses 101a and 101b is more obliquely incident upon a pixel 102a located in the vicinity of an end of the solid-state image pickup device 102 as compared with a pixel 102b located in the vicinity of the central portion of the solid-state image pickup device 102. In the solid-state image pickup device 102 according to the first exemplary prior art shown in FIG. 29, as hereinabove described, it is so difficult to condense light obliquely incident upon the lens 109 on the center of the corresponding photodetection part 105 that it is disadvantageously difficult to improve condensation efficiency of the lens 109 for the corresponding photodetection part 105 in the vicinity of an end of the photodetection region receiving the obliquely incident light. Thus, it is problematically difficult to improve the photosensitivity of the solid-state image pickup device 102.
Also in the solid-state image pickup device 122 according to the second exemplary prior art shown in FIG. 30, the lens center 119a of the lens 119 so coincides with the center of the photodetection part 105 that it is disadvantageously difficult to condense light obliquely incident upon the lens 119 on the center of the photodetection part 105, as shown in FIG. 33. Thus, it is problematically difficult to improve the photosensitivity of the solid-state image pickup device 122 in the vicinity of an end of a photodetection region receiving more obliquely incident light as compared with the vicinity of the central portion of the photodetection region, similarly to the solid-state image pickup device 102 according to the first exemplary prior art shown in FIG. 29.